Recently, in line with portable, miniaturization, lightweight, and high-performance trends in electronic devices, electronics, information and telecommunications industries have rapidly grown. Accordingly, high-performance lithium secondary batteries are being used as power sources of these portable electronic devices, and the demand therefor is being rapidly increased. Secondary batteries, which can be repeatedly used by being charged and discharged, are essential for power sources of portable electronic devices for information and telecommunication, electric bikes, or electric vehicles. In particular, since the performance of these products may depend on batteries as a key component, customer demand for high-capacity batteries is being increased.
In general, it is known that battery safety improves in the order of a liquid electrolyte, a gel polymer electrolyte, and a solid polymer electrolyte, but battery performance decreases in the same order.
An electrolyte in a liquid state, particularly, an ion conductive organic liquid electrolyte, in which a salt is dissolved in a non-aqueous organic solvent, has been mainly used as an electrolyte for an electrochemical device, such as a typical battery using an electrochemical reaction and an electric double-layer capacitor. However, when the electrolyte in a liquid state is used, an electrode material may degrade and the organic solvent is likely to be volatilized. Also, there may be limitations in safety such as combustion due to ambient temperature and the temperature rise of the battery itself.
It is known that the solid polymer electrolyte has not been commercialized yet due to poor battery performance.
Since the gel polymer electrolyte may have excellent electrochemical safety, the thickness of the battery may be constantly maintained. Furthermore, since a contact between an electrode and the electrolyte may be excellent due to the inherent adhesion of a gel phase, a thin-film type battery may be prepared. Thus, the development of various gel polymer electrolytes is being expanded.
In the gel polymer electrolyte, since the size of lithium ions may be small, direct movement may not only be relatively easy, but also the lithium ions may easily move in the electrolyte solution due to a hopping phenomenon as illustrated in FIG. 1.
When the metal ions are dissolved, the metal ions may be reduced to a metallic state in an anode to block reaction sites of the anode. When the new metal is precipitated on the surface of the anode, an electrolyte solution produces a new solid electrolyte interface (SEI) layer on the surface of the metal, and thus, the electrolyte solution is continuously consumed. Also, since the thickness of the SEI layer in the anode may be continuously increased to increase resistance, life characteristics of the lithium secondary battery may be decreased. Thus, there is a need to improve the above limitations.